A method for producing an ashless coal is disclosed in Patent Document 1. In such a production method, a raw material coal as a mixture of steam coal and caking coal is mixed with a solvent to prepare a slurry, and the slurry thus prepared is heated, thereby extracting coal components soluble in the solvent, then the gravitational settling method is applied to the slurry in which the coal components has been extracted, thereby separating the slurry into a solution which contains the coal components soluble in the solvent and a solid-content concentrated slurry containing coal components insoluble in the solvent, and further the removal of the solvent from the separated solution is carried out, thereby obtaining an ashless coal. In addition, the solvent is separated from the separated solid-content concentrated slurry, thereby obtaining a by-product coal.
An ashless coal and a by-product coal are present as a solute in an organic solvent in its production process, but convert to a solid state when a solvent has removed, followed by cooling. Patent Document 2 discloses a spray drying method of spraying a preheated solution to a collection plate provided in a main body container from a spray nozzle to evaporate a solvent in the solution by heat transfer from the collection plate as a method for removing (recovering) a solvent. Patent Document 3 discloses a solvent recovering method of dispersing a solution toward an inner wall heated in a solvent separation tower using a rotary dispersion mechanism rotating the solvent, thereby volatilizing a solvent in the solution.